The Sea Elves' Blessing

A terrible tyrant ruler had gained power, but a group of elves came to understand that if they worked together they could depose her. They organized in secret, but one in their ranks grew fearful and betrayed their plans to the ruler to save himself.
Immediately, the ruler ordered the elves to be put to death, without the rest of her subjects knowing. She knew that they were right, and that if too many united against her resistance would be impossible. The elves were put on a ship and brought out to the deepest part of the ocean known at the time. The elves were thrown overboard and left to drown. The traitor, for his part, was not sent to sea with his former comrades and was simply executed for participating in the conspiracy.
However, Marinus saw the plight of these elves and did not believe they had done anything wrong in defying the tyrant. Much as fish school together and are stronger for their unity, the elves had come together and grown stronger for it. So Marinus blessed the elves with the ability to live underwater, and they did not drown.
These new sea elves returned to the place whence they came and helped their former neighbors to throw off the yoke of the tyrant's rule. Some remained in their old home, but most embraced their blessing fully and returned to live in the sea.